… | |
… | |
21 | # data was decoded |
21 | # data was decoded |
22 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
22 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
23 | } |
23 | } |
24 | |
24 | |
25 | DESCRIPTION |
25 | DESCRIPTION |
26 | WARNING! THIS IS A PRE-ALPHA RELEASE! IT WILL CRASH, CORRUPT YOUR DATA |
|
|
27 | AND EAT YOUR CHILDREN! (Actually, apart from being untested and a bit |
|
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28 | feature-limited, it might already be useful). |
|
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29 | |
|
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30 | This module converts Perl data structures to the Concise Binary Object |
26 | This module converts Perl data structures to the Concise Binary Object |
31 | Representation (CBOR) and vice versa. CBOR is a fast binary |
27 | Representation (CBOR) and vice versa. CBOR is a fast binary |
32 | serialisation format that aims to use a superset of the JSON data model, |
28 | serialisation format that aims to use an (almost) superset of the JSON |
33 | i.e. when you can represent something in JSON, you should be able to |
29 | data model, i.e. when you can represent something useful in JSON, you |
34 | represent it in CBOR. |
30 | should be able to represent it in CBOR. |
35 | |
31 | |
36 | This makes it a faster and more compact binary alternative to JSON, with |
32 | In short, CBOR is a faster and quite compact binary alternative to JSON, |
37 | the added ability of supporting serialising of perl objects. |
33 | with the added ability of supporting serialisation of Perl objects. |
|
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34 | (JSON often compresses better than CBOR though, so if you plan to |
|
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35 | compress the data later and speed is less important you might want to |
|
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36 | compare both formats first). |
|
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37 | |
|
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38 | To give you a general idea about speed, with texts in the megabyte |
|
|
39 | range, "CBOR::XS" usually encodes roughly twice as fast as Storable or |
|
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40 | JSON::XS and decodes about 15%-30% faster than those. The shorter the |
|
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41 | data, the worse Storable performs in comparison. |
|
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42 | |
|
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43 | Regarding compactness, "CBOR::XS"-encoded data structures are usually |
|
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44 | about 20% smaller than the same data encoded as (compact) JSON or |
|
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45 | Storable. |
|
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46 | |
|
|
47 | In addition to the core CBOR data format, this module implements a |
|
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48 | number of extensions, to support cyclic and shared data structures (see |
|
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49 | "allow_sharing" and "allow_cycles"), string deduplication (see |
|
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50 | "pack_strings") and scalar references (always enabled). |
38 | |
51 | |
39 | The primary goal of this module is to be *correct* and the secondary |
52 | The primary goal of this module is to be *correct* and the secondary |
40 | goal is to be *fast*. To reach the latter goal it was written in C. |
53 | goal is to be *fast*. To reach the latter goal it was written in C. |
41 | |
54 | |
42 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
55 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
… | |
… | |
64 | *disabled*. |
77 | *disabled*. |
65 | |
78 | |
66 | The mutators for flags all return the CBOR object again and thus |
79 | The mutators for flags all return the CBOR object again and thus |
67 | calls can be chained: |
80 | calls can be chained: |
68 | |
81 | |
69 | #TODO my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
82 | my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
70 | |
83 | |
71 | $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
84 | $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
72 | $max_depth = $cbor->get_max_depth |
85 | $max_depth = $cbor->get_max_depth |
73 | Sets the maximum nesting level (default 512) accepted while encoding |
86 | Sets the maximum nesting level (default 512) accepted while encoding |
74 | or decoding. If a higher nesting level is detected in CBOR data or a |
87 | or decoding. If a higher nesting level is detected in CBOR data or a |
… | |
… | |
105 | as when 0 is specified). |
118 | as when 0 is specified). |
106 | |
119 | |
107 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
120 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
108 | useful. |
121 | useful. |
109 | |
122 | |
|
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123 | $cbor = $cbor->allow_unknown ([$enable]) |
|
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124 | $enabled = $cbor->get_allow_unknown |
|
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125 | If $enable is true (or missing), then "encode" will *not* throw an |
|
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126 | exception when it encounters values it cannot represent in CBOR (for |
|
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127 | example, filehandles) but instead will encode a CBOR "error" value. |
|
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128 | |
|
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129 | If $enable is false (the default), then "encode" will throw an |
|
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130 | exception when it encounters anything it cannot encode as CBOR. |
|
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131 | |
|
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132 | This option does not affect "decode" in any way, and it is |
|
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133 | recommended to leave it off unless you know your communications |
|
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134 | partner. |
|
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135 | |
|
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136 | $cbor = $cbor->allow_sharing ([$enable]) |
|
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137 | $enabled = $cbor->get_allow_sharing |
|
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138 | If $enable is true (or missing), then "encode" will not |
|
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139 | double-encode values that have been referenced before (e.g. when the |
|
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140 | same object, such as an array, is referenced multiple times), but |
|
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141 | instead will emit a reference to the earlier value. |
|
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142 | |
|
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143 | This means that such values will only be encoded once, and will not |
|
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144 | result in a deep cloning of the value on decode, in decoders |
|
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145 | supporting the value sharing extension. This also makes it possible |
|
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146 | to encode cyclic data structures (which need "allow_cycles" to ne |
|
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147 | enabled to be decoded by this module). |
|
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148 | |
|
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149 | It is recommended to leave it off unless you know your communication |
|
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150 | partner supports the value sharing extensions to CBOR |
|
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151 | (<http://cbor.schmorp.de/value-sharing>), as without decoder |
|
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152 | support, the resulting data structure might be unusable. |
|
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153 | |
|
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154 | Detecting shared values incurs a runtime overhead when values are |
|
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155 | encoded that have a reference counter large than one, and might |
|
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156 | unnecessarily increase the encoded size, as potentially shared |
|
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157 | values are encode as shareable whether or not they are actually |
|
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158 | shared. |
|
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159 | |
|
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160 | At the moment, only targets of references can be shared (e.g. |
|
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161 | scalars, arrays or hashes pointed to by a reference). Weirder |
|
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162 | constructs, such as an array with multiple "copies" of the *same* |
|
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163 | string, which are hard but not impossible to create in Perl, are not |
|
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164 | supported (this is the same as with Storable). |
|
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165 | |
|
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166 | If $enable is false (the default), then "encode" will encode shared |
|
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167 | data structures repeatedly, unsharing them in the process. Cyclic |
|
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168 | data structures cannot be encoded in this mode. |
|
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169 | |
|
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170 | This option does not affect "decode" in any way - shared values and |
|
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171 | references will always be decoded properly if present. |
|
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172 | |
|
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173 | $cbor = $cbor->allow_cycles ([$enable]) |
|
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174 | $enabled = $cbor->get_allow_cycles |
|
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175 | If $enable is true (or missing), then "decode" will happily decode |
|
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176 | self-referential (cyclic) data structures. By default these will not |
|
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177 | be decoded, as they need manual cleanup to avoid memory leaks, so |
|
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178 | code that isn't prepared for this will not leak memory. |
|
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179 | |
|
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180 | If $enable is false (the default), then "decode" will throw an error |
|
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181 | when it encounters a self-referential/cyclic data structure. |
|
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182 | |
|
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183 | FUTURE DIRECTION: the motivation behind this option is to avoid |
|
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184 | *real* cycles - future versions of this module might chose to decode |
|
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185 | cyclic data structures using weak references when this option is |
|
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186 | off, instead of throwing an error. |
|
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187 | |
|
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188 | This option does not affect "encode" in any way - shared values and |
|
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189 | references will always be encoded properly if present. |
|
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190 | |
|
|
191 | $cbor = $cbor->pack_strings ([$enable]) |
|
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192 | $enabled = $cbor->get_pack_strings |
|
|
193 | If $enable is true (or missing), then "encode" will try not to |
|
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194 | encode the same string twice, but will instead encode a reference to |
|
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195 | the string instead. Depending on your data format, this can save a |
|
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196 | lot of space, but also results in a very large runtime overhead |
|
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197 | (expect encoding times to be 2-4 times as high as without). |
|
|
198 | |
|
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199 | It is recommended to leave it off unless you know your |
|
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200 | communications partner supports the stringref extension to CBOR |
|
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201 | (<http://cbor.schmorp.de/stringref>), as without decoder support, |
|
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202 | the resulting data structure might not be usable. |
|
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203 | |
|
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204 | If $enable is false (the default), then "encode" will encode strings |
|
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205 | the standard CBOR way. |
|
|
206 | |
|
|
207 | This option does not affect "decode" in any way - string references |
|
|
208 | will always be decoded properly if present. |
|
|
209 | |
|
|
210 | $cbor = $cbor->text_keys ([$enable]) |
|
|
211 | $enabled = $cbor->get_text_keys |
|
|
212 | If $enabled is true (or missing), then "encode" will encode all perl |
|
|
213 | hash keys as CBOR text strings/UTF-8 string, upgrading them as |
|
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214 | needed. |
|
|
215 | |
|
|
216 | If $enable is false (the default), then "encode" will encode hash |
|
|
217 | keys normally - upgraded perl strings (strings internally encoded as |
|
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218 | UTF-8) as CBOR text strings, and downgraded perl strings as CBOR |
|
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219 | byte strings. |
|
|
220 | |
|
|
221 | This option does not affect "decode" in any way. |
|
|
222 | |
|
|
223 | This option is useful for interoperability with CBOR decoders that |
|
|
224 | don't treat byte strings as a form of text. It is especially useful |
|
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225 | as Perl gives very little control over hash keys. |
|
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226 | |
|
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227 | Enabling this option can be slow, as all downgraded hash keys that |
|
|
228 | are encoded need to be scanned and converted to UTF-8. |
|
|
229 | |
|
|
230 | $cbor = $cbor->text_strings ([$enable]) |
|
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231 | $enabled = $cbor->get_text_strings |
|
|
232 | This option works similar to "text_keys", above, but works on all |
|
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233 | strings (including hash keys), so "text_keys" has no further effect |
|
|
234 | after enabling "text_strings". |
|
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235 | |
|
|
236 | If $enabled is true (or missing), then "encode" will encode all perl |
|
|
237 | strings as CBOR text strings/UTF-8 strings, upgrading them as |
|
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238 | needed. |
|
|
239 | |
|
|
240 | If $enable is false (the default), then "encode" will encode strings |
|
|
241 | normally (but see "text_keys") - upgraded perl strings (strings |
|
|
242 | internally encoded as UTF-8) as CBOR text strings, and downgraded |
|
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243 | perl strings as CBOR byte strings. |
|
|
244 | |
|
|
245 | This option does not affect "decode" in any way. |
|
|
246 | |
|
|
247 | This option has similar advantages and disadvantages as "text_keys". |
|
|
248 | In addition, this option effectively removes the ability to encode |
|
|
249 | byte strings, which might break some "FREEZE" and "TO_CBOR" methods |
|
|
250 | that rely on this, such as bignum encoding, so this option is mainly |
|
|
251 | useful for very simple data. |
|
|
252 | |
|
|
253 | $cbor = $cbor->validate_utf8 ([$enable]) |
|
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254 | $enabled = $cbor->get_validate_utf8 |
|
|
255 | If $enable is true (or missing), then "decode" will validate that |
|
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256 | elements (text strings) containing UTF-8 data in fact contain valid |
|
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257 | UTF-8 data (instead of blindly accepting it). This validation |
|
|
258 | obviously takes extra time during decoding. |
|
|
259 | |
|
|
260 | The concept of "valid UTF-8" used is perl's concept, which is a |
|
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261 | superset of the official UTF-8. |
|
|
262 | |
|
|
263 | If $enable is false (the default), then "decode" will blindly accept |
|
|
264 | UTF-8 data, marking them as valid UTF-8 in the resulting data |
|
|
265 | structure regardless of whether that's true or not. |
|
|
266 | |
|
|
267 | Perl isn't too happy about corrupted UTF-8 in strings, but should |
|
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268 | generally not crash or do similarly evil things. Extensions might be |
|
|
269 | not so forgiving, so it's recommended to turn on this setting if you |
|
|
270 | receive untrusted CBOR. |
|
|
271 | |
|
|
272 | This option does not affect "encode" in any way - strings that are |
|
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273 | supposedly valid UTF-8 will simply be dumped into the resulting CBOR |
|
|
274 | string without checking whether that is, in fact, true or not. |
|
|
275 | |
|
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276 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
|
|
277 | $cb_or_undef = $cbor->get_filter |
|
|
278 | Sets or replaces the tagged value decoding filter (when $cb is |
|
|
279 | specified) or clears the filter (if no argument or "undef" is |
|
|
280 | provided). |
|
|
281 | |
|
|
282 | The filter callback is called only during decoding, when a |
|
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283 | non-enforced tagged value has been decoded (see "TAG HANDLING AND |
|
|
284 | EXTENSIONS" for a list of enforced tags). For specific tags, it's |
|
|
285 | often better to provide a default converter using the |
|
|
286 | %CBOR::XS::FILTER hash (see below). |
|
|
287 | |
|
|
288 | The first argument is the numerical tag, the second is the (decoded) |
|
|
289 | value that has been tagged. |
|
|
290 | |
|
|
291 | The filter function should return either exactly one value, which |
|
|
292 | will replace the tagged value in the decoded data structure, or no |
|
|
293 | values, which will result in default handling, which currently means |
|
|
294 | the decoder creates a "CBOR::XS::Tagged" object to hold the tag and |
|
|
295 | the value. |
|
|
296 | |
|
|
297 | When the filter is cleared (the default state), the default filter |
|
|
298 | function, "CBOR::XS::default_filter", is used. This function simply |
|
|
299 | looks up the tag in the %CBOR::XS::FILTER hash. If an entry exists |
|
|
300 | it must be a code reference that is called with tag and value, and |
|
|
301 | is responsible for decoding the value. If no entry exists, it |
|
|
302 | returns no values. |
|
|
303 | |
|
|
304 | Example: decode all tags not handled internally into |
|
|
305 | "CBOR::XS::Tagged" objects, with no other special handling (useful |
|
|
306 | when working with potentially "unsafe" CBOR data). |
|
|
307 | |
|
|
308 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
|
|
309 | |
|
|
310 | Example: provide a global filter for tag 1347375694, converting the |
|
|
311 | value into some string form. |
|
|
312 | |
|
|
313 | $CBOR::XS::FILTER{1347375694} = sub { |
|
|
314 | my ($tag, $value); |
|
|
315 | |
|
|
316 | "tag 1347375694 value $value" |
|
|
317 | }; |
|
|
318 | |
110 | $cbor_data = $cbor->encode ($perl_scalar) |
319 | $cbor_data = $cbor->encode ($perl_scalar) |
111 | Converts the given Perl data structure (a scalar value) to its CBOR |
320 | Converts the given Perl data structure (a scalar value) to its CBOR |
112 | representation. |
321 | representation. |
113 | |
322 | |
114 | $perl_scalar = $cbor->decode ($cbor_data) |
323 | $perl_scalar = $cbor->decode ($cbor_data) |
… | |
… | |
126 | the next one starts. |
335 | the next one starts. |
127 | |
336 | |
128 | CBOR::XS->new->decode_prefix ("......") |
337 | CBOR::XS->new->decode_prefix ("......") |
129 | => ("...", 3) |
338 | => ("...", 3) |
130 | |
339 | |
|
|
340 | INCREMENTAL PARSING |
|
|
341 | In some cases, there is the need for incremental parsing of JSON texts. |
|
|
342 | While this module always has to keep both CBOR text and resulting Perl |
|
|
343 | data structure in memory at one time, it does allow you to parse a CBOR |
|
|
344 | stream incrementally, using a similar to using "decode_prefix" to see if |
|
|
345 | a full CBOR object is available, but is much more efficient. |
|
|
346 | |
|
|
347 | It basically works by parsing as much of a CBOR string as possible - if |
|
|
348 | the CBOR data is not complete yet, the pasrer will remember where it |
|
|
349 | was, to be able to restart when more data has been accumulated. Once |
|
|
350 | enough data is available to either decode a complete CBOR value or raise |
|
|
351 | an error, a real decode will be attempted. |
|
|
352 | |
|
|
353 | A typical use case would be a network protocol that consists of sending |
|
|
354 | and receiving CBOR-encoded messages. The solution that works with CBOR |
|
|
355 | and about anything else is by prepending a length to every CBOR value, |
|
|
356 | so the receiver knows how many octets to read. More compact (and |
|
|
357 | slightly slower) would be to just send CBOR values back-to-back, as |
|
|
358 | "CBOR::XS" knows where a CBOR value ends, and doesn't need an explicit |
|
|
359 | length. |
|
|
360 | |
|
|
361 | The following methods help with this: |
|
|
362 | |
|
|
363 | @decoded = $cbor->incr_parse ($buffer) |
|
|
364 | This method attempts to decode exactly one CBOR value from the |
|
|
365 | beginning of the given $buffer. The value is removed from the |
|
|
366 | $buffer on success. When $buffer doesn't contain a complete value |
|
|
367 | yet, it returns nothing. Finally, when the $buffer doesn't start |
|
|
368 | with something that could ever be a valid CBOR value, it raises an |
|
|
369 | exception, just as "decode" would. In the latter case the decoder |
|
|
370 | state is undefined and must be reset before being able to parse |
|
|
371 | further. |
|
|
372 | |
|
|
373 | This method modifies the $buffer in place. When no CBOR value can be |
|
|
374 | decoded, the decoder stores the current string offset. On the next |
|
|
375 | call, continues decoding at the place where it stopped before. For |
|
|
376 | this to make sense, the $buffer must begin with the same octets as |
|
|
377 | on previous unsuccessful calls. |
|
|
378 | |
|
|
379 | You can call this method in scalar context, in which case it either |
|
|
380 | returns a decoded value or "undef". This makes it impossible to |
|
|
381 | distinguish between CBOR null values (which decode to "undef") and |
|
|
382 | an unsuccessful decode, which is often acceptable. |
|
|
383 | |
|
|
384 | @decoded = $cbor->incr_parse_multiple ($buffer) |
|
|
385 | Same as "incr_parse", but attempts to decode as many CBOR values as |
|
|
386 | possible in one go, instead of at most one. Calls to "incr_parse" |
|
|
387 | and "incr_parse_multiple" can be interleaved. |
|
|
388 | |
|
|
389 | $cbor->incr_reset |
|
|
390 | Resets the incremental decoder. This throws away any saved state, so |
|
|
391 | that subsequent calls to "incr_parse" or "incr_parse_multiple" start |
|
|
392 | to parse a new CBOR value from the beginning of the $buffer again. |
|
|
393 | |
|
|
394 | This method can be caled at any time, but it *must* be called if you |
|
|
395 | want to change your $buffer or there was a decoding error and you |
|
|
396 | want to reuse the $cbor object for future incremental parsings. |
|
|
397 | |
131 | MAPPING |
398 | MAPPING |
132 | This section describes how CBOR::XS maps Perl values to CBOR values and |
399 | This section describes how CBOR::XS maps Perl values to CBOR values and |
133 | vice versa. These mappings are designed to "do the right thing" in most |
400 | vice versa. These mappings are designed to "do the right thing" in most |
134 | circumstances automatically, preserving round-tripping characteristics |
401 | circumstances automatically, preserving round-tripping characteristics |
135 | (what you put in comes out as something equivalent). |
402 | (what you put in comes out as something equivalent). |
… | |
… | |
142 | integers |
409 | integers |
143 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
410 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
144 | support, 64 bit integers will be truncated or otherwise corrupted. |
411 | support, 64 bit integers will be truncated or otherwise corrupted. |
145 | |
412 | |
146 | byte strings |
413 | byte strings |
147 | Byte strings will become octet strings in Perl (the byte values |
414 | Byte strings will become octet strings in Perl (the Byte values |
148 | 0..255 will simply become characters of the same value in Perl). |
415 | 0..255 will simply become characters of the same value in Perl). |
149 | |
416 | |
150 | UTF-8 strings |
417 | UTF-8 strings |
151 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
418 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
152 | decoded into proper Unicode code points. At the moment, the validity |
419 | decoded into proper Unicode code points. At the moment, the validity |
… | |
… | |
166 | "Types:Serialiser::false" and "Types::Serialiser::error", |
433 | "Types:Serialiser::false" and "Types::Serialiser::error", |
167 | respectively. They are overloaded to act almost exactly like the |
434 | respectively. They are overloaded to act almost exactly like the |
168 | numbers 1 and 0 (for true and false) or to throw an exception on |
435 | numbers 1 and 0 (for true and false) or to throw an exception on |
169 | access (for error). See the Types::Serialiser manpage for details. |
436 | access (for error). See the Types::Serialiser manpage for details. |
170 | |
437 | |
171 | CBOR tag 256 (perl object) |
438 | tagged values |
172 | The tag value 256 (TODO: pending iana registration) will be used to |
|
|
173 | deserialise a Perl object serialised with "FREEZE". See "OBJECT |
|
|
174 | SERIALISATION", below, for details. |
|
|
175 | |
|
|
176 | CBOR tag 55799 (magic header) |
|
|
177 | The tag 55799 is ignored (this tag implements the magic header). |
|
|
178 | |
|
|
179 | other CBOR tags |
|
|
180 | Tagged items consists of a numeric tag and another CBOR value. Tags |
439 | Tagged items consists of a numeric tag and another CBOR value. |
181 | not handled internally are currently converted into a |
|
|
182 | CBOR::XS::Tagged object, which is simply a blessed array reference |
|
|
183 | consisting of the numeric tag value followed by the (decoded) CBOR |
|
|
184 | value. |
|
|
185 | |
440 | |
186 | In the future, support for user-supplied conversions might get |
441 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
187 | added. |
442 | for details on which tags are handled how. |
188 | |
443 | |
189 | anything else |
444 | anything else |
190 | Anything else (e.g. unsupported simple values) will raise a decoding |
445 | Anything else (e.g. unsupported simple values) will raise a decoding |
191 | error. |
446 | error. |
192 | |
447 | |
193 | PERL -> CBOR |
448 | PERL -> CBOR |
194 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
449 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
195 | truly typeless language, so we can only guess which CBOR type is meant |
450 | typeless language. That means this module can only guess which CBOR type |
196 | by a Perl value. |
451 | is meant by a perl value. |
197 | |
452 | |
198 | hash references |
453 | hash references |
199 | Perl hash references become CBOR maps. As there is no inherent |
454 | Perl hash references become CBOR maps. As there is no inherent |
200 | ordering in hash keys (or CBOR maps), they will usually be encoded |
455 | ordering in hash keys (or CBOR maps), they will usually be encoded |
201 | in a pseudo-random order. |
456 | in a pseudo-random order. This order can be different each time a |
|
|
457 | hash is encoded. |
202 | |
458 | |
203 | Currently, tied hashes will use the indefinite-length format, while |
459 | Currently, tied hashes will use the indefinite-length format, while |
204 | normal hashes will use the fixed-length format. |
460 | normal hashes will use the fixed-length format. |
205 | |
461 | |
206 | array references |
462 | array references |
207 | Perl array references become fixed-length CBOR arrays. |
463 | Perl array references become fixed-length CBOR arrays. |
208 | |
464 | |
209 | other references |
465 | other references |
210 | Other unblessed references are generally not allowed and will cause |
466 | Other unblessed references will be represented using the indirection |
211 | an exception to be thrown, except for references to the integers 0 |
467 | tag extension (tag value 22098, |
212 | and 1, which get turned into false and true in CBOR. |
468 | <http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
|
|
469 | to be able to decode these values somehow, by either "doing the |
|
|
470 | right thing", decoding into a generic tagged object, simply ignoring |
|
|
471 | the tag, or something else. |
213 | |
472 | |
214 | CBOR::XS::Tagged objects |
473 | CBOR::XS::Tagged objects |
215 | Objects of this type must be arrays consisting of a single "[tag, |
474 | Objects of this type must be arrays consisting of a single "[tag, |
216 | value]" pair. The (numerical) tag will be encoded as a CBOR tag, the |
475 | value]" pair. The (numerical) tag will be encoded as a CBOR tag, the |
217 | value will be encoded as appropriate for the value. |
476 | value will be encoded as appropriate for the value. You must use |
|
|
477 | "CBOR::XS::tag" to create such objects. |
218 | |
478 | |
219 | Types::Serialiser::true, Types::Serialiser::false, |
479 | Types::Serialiser::true, Types::Serialiser::false, |
220 | Types::Serialiser::error |
480 | Types::Serialiser::error |
221 | These special values become CBOR true, CBOR false and CBOR undefined |
481 | These special values become CBOR true, CBOR false and CBOR undefined |
222 | values, respectively. You can also use "\1", "\0" and "\undef" |
482 | values, respectively. You can also use "\1", "\0" and "\undef" |
223 | directly if you want. |
483 | directly if you want. |
224 | |
484 | |
225 | other blessed objects |
485 | other blessed objects |
226 | Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See |
486 | Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See |
227 | "OBJECT SERIALISATION", below, for details. |
487 | "TAG HANDLING AND EXTENSIONS" for specific classes handled by this |
|
|
488 | module, and "OBJECT SERIALISATION" for generic object serialisation. |
228 | |
489 | |
229 | simple scalars |
490 | simple scalars |
230 | TODO Simple Perl scalars (any scalar that is not a reference) are |
491 | Simple Perl scalars (any scalar that is not a reference) are the |
231 | the most difficult objects to encode: CBOR::XS will encode undefined |
492 | most difficult objects to encode: CBOR::XS will encode undefined |
232 | scalars as CBOR null values, scalars that have last been used in a |
493 | scalars as CBOR null values, scalars that have last been used in a |
233 | string context before encoding as CBOR strings, and anything else as |
494 | string context before encoding as CBOR strings, and anything else as |
234 | number value: |
495 | number value: |
235 | |
496 | |
236 | # dump as number |
497 | # dump as number |
237 | encode_cbor [2] # yields [2] |
498 | encode_cbor [2] # yields [2] |
238 | encode_cbor [-3.0e17] # yields [-3e+17] |
499 | encode_cbor [-3.0e17] # yields [-3e+17] |
239 | my $value = 5; encode_cbor [$value] # yields [5] |
500 | my $value = 5; encode_cbor [$value] # yields [5] |
240 | |
501 | |
241 | # used as string, so dump as string |
502 | # used as string, so dump as string (either byte or text) |
242 | print $value; |
503 | print $value; |
243 | encode_cbor [$value] # yields ["5"] |
504 | encode_cbor [$value] # yields ["5"] |
244 | |
505 | |
245 | # undef becomes null |
506 | # undef becomes null |
246 | encode_cbor [undef] # yields [null] |
507 | encode_cbor [undef] # yields [null] |
… | |
… | |
249 | |
510 | |
250 | my $x = 3.1; # some variable containing a number |
511 | my $x = 3.1; # some variable containing a number |
251 | "$x"; # stringified |
512 | "$x"; # stringified |
252 | $x .= ""; # another, more awkward way to stringify |
513 | $x .= ""; # another, more awkward way to stringify |
253 | print $x; # perl does it for you, too, quite often |
514 | print $x; # perl does it for you, too, quite often |
|
|
515 | |
|
|
516 | You can force whether a string is encoded as byte or text string by |
|
|
517 | using "utf8::upgrade" and "utf8::downgrade" (if "text_strings" is |
|
|
518 | disabled): |
|
|
519 | |
|
|
520 | utf8::upgrade $x; # encode $x as text string |
|
|
521 | utf8::downgrade $x; # encode $x as byte string |
|
|
522 | |
|
|
523 | Perl doesn't define what operations up- and downgrade strings, so if |
|
|
524 | the difference between byte and text is important, you should up- or |
|
|
525 | downgrade your string as late as possible before encoding. You can |
|
|
526 | also force the use of CBOR text strings by using "text_keys" or |
|
|
527 | "text_strings". |
254 | |
528 | |
255 | You can force the type to be a CBOR number by numifying it: |
529 | You can force the type to be a CBOR number by numifying it: |
256 | |
530 | |
257 | my $x = "3"; # some variable containing a string |
531 | my $x = "3"; # some variable containing a string |
258 | $x += 0; # numify it, ensuring it will be dumped as a number |
532 | $x += 0; # numify it, ensuring it will be dumped as a number |
… | |
… | |
268 | the IEEE double format will be used. Perls that use formats other |
542 | the IEEE double format will be used. Perls that use formats other |
269 | than IEEE double to represent numerical values are supported, but |
543 | than IEEE double to represent numerical values are supported, but |
270 | might suffer loss of precision. |
544 | might suffer loss of precision. |
271 | |
545 | |
272 | OBJECT SERIALISATION |
546 | OBJECT SERIALISATION |
|
|
547 | This module implements both a CBOR-specific and the generic |
|
|
548 | Types::Serialier object serialisation protocol. The following |
|
|
549 | subsections explain both methods. |
|
|
550 | |
|
|
551 | ENCODING |
273 | This module knows two way to serialise a Perl object: The CBOR-specific |
552 | This module knows two way to serialise a Perl object: The CBOR-specific |
274 | way, and the generic way. |
553 | way, and the generic way. |
275 | |
554 | |
276 | Whenever the encoder encounters a Perl object that it cnanot serialise |
555 | Whenever the encoder encounters a Perl object that it cannot serialise |
277 | directly (most of them), it will first look up the "TO_CBOR" method on |
556 | directly (most of them), it will first look up the "TO_CBOR" method on |
278 | it. |
557 | it. |
279 | |
558 | |
280 | If it has a "TO_CBOR" method, it will call it with the object as only |
559 | If it has a "TO_CBOR" method, it will call it with the object as only |
281 | argument, and expects exactly one return value, which it will then |
560 | argument, and expects exactly one return value, which it will then |
… | |
… | |
286 | "CBOR" as the second argument, to distinguish it from other serialisers. |
565 | "CBOR" as the second argument, to distinguish it from other serialisers. |
287 | |
566 | |
288 | The "FREEZE" method can return any number of values (i.e. zero or more). |
567 | The "FREEZE" method can return any number of values (i.e. zero or more). |
289 | These will be encoded as CBOR perl object, together with the classname. |
568 | These will be encoded as CBOR perl object, together with the classname. |
290 | |
569 | |
|
|
570 | These methods *MUST NOT* change the data structure that is being |
|
|
571 | serialised. Failure to comply to this can result in memory corruption - |
|
|
572 | and worse. |
|
|
573 | |
291 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
574 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
292 | with an error. |
575 | with an error. |
293 | |
576 | |
|
|
577 | DECODING |
294 | Objects encoded via "TO_CBOR" cannot be automatically decoded, but |
578 | Objects encoded via "TO_CBOR" cannot (normally) be automatically |
295 | objects encoded via "FREEZE" can be decoded using the following |
579 | decoded, but objects encoded via "FREEZE" can be decoded using the |
296 | protocol: |
580 | following protocol: |
297 | |
581 | |
298 | When an encoded CBOR perl object is encountered by the decoder, it will |
582 | When an encoded CBOR perl object is encountered by the decoder, it will |
299 | look up the "THAW" method, by using the stored classname, and will fail |
583 | look up the "THAW" method, by using the stored classname, and will fail |
300 | if the method cannot be found. |
584 | if the method cannot be found. |
301 | |
585 | |
… | |
… | |
322 | |
606 | |
323 | sub URI::TO_CBOR { |
607 | sub URI::TO_CBOR { |
324 | my ($self) = @_; |
608 | my ($self) = @_; |
325 | my $uri = "$self"; # stringify uri |
609 | my $uri = "$self"; # stringify uri |
326 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
610 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
327 | CBOR::XS::tagged 32, "$_[0]" |
611 | CBOR::XS::tag 32, "$_[0]" |
328 | } |
612 | } |
329 | |
613 | |
330 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
614 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
331 | URI. |
615 | URI. |
332 | |
616 | |
… | |
… | |
343 | "$self" # encode url string |
627 | "$self" # encode url string |
344 | } |
628 | } |
345 | |
629 | |
346 | sub URI::THAW { |
630 | sub URI::THAW { |
347 | my ($class, $serialiser, $uri) = @_; |
631 | my ($class, $serialiser, $uri) = @_; |
348 | |
|
|
349 | $class->new ($uri) |
632 | $class->new ($uri) |
350 | } |
633 | } |
351 | |
634 | |
352 | Unlike "TO_CBOR", multiple values can be returned by "FREEZE". For |
635 | Unlike "TO_CBOR", multiple values can be returned by "FREEZE". For |
353 | example, a "FREEZE" method that returns "type", "id" and "variant" |
636 | example, a "FREEZE" method that returns "type", "id" and "variant" |
… | |
… | |
367 | |
650 | |
368 | MAGIC HEADER |
651 | MAGIC HEADER |
369 | There is no way to distinguish CBOR from other formats programmatically. |
652 | There is no way to distinguish CBOR from other formats programmatically. |
370 | To make it easier to distinguish CBOR from other formats, the CBOR |
653 | To make it easier to distinguish CBOR from other formats, the CBOR |
371 | specification has a special "magic string" that can be prepended to any |
654 | specification has a special "magic string" that can be prepended to any |
372 | CBOR string without changing it's meaning. |
655 | CBOR string without changing its meaning. |
373 | |
656 | |
374 | This string is available as $CBOR::XS::MAGIC. This module does not |
657 | This string is available as $CBOR::XS::MAGIC. This module does not |
375 | prepend this string tot he CBOR data it generates, but it will ignroe it |
658 | prepend this string to the CBOR data it generates, but it will ignore it |
376 | if present, so users can prepend this string as a "file type" indicator |
659 | if present, so users can prepend this string as a "file type" indicator |
377 | as required. |
660 | as required. |
|
|
661 | |
|
|
662 | THE CBOR::XS::Tagged CLASS |
|
|
663 | CBOR has the concept of tagged values - any CBOR value can be tagged |
|
|
664 | with a numeric 64 bit number, which are centrally administered. |
|
|
665 | |
|
|
666 | "CBOR::XS" handles a few tags internally when en- or decoding. You can |
|
|
667 | also create tags yourself by encoding "CBOR::XS::Tagged" objects, and |
|
|
668 | the decoder will create "CBOR::XS::Tagged" objects itself when it hits |
|
|
669 | an unknown tag. |
|
|
670 | |
|
|
671 | These objects are simply blessed array references - the first member of |
|
|
672 | the array being the numerical tag, the second being the value. |
|
|
673 | |
|
|
674 | You can interact with "CBOR::XS::Tagged" objects in the following ways: |
|
|
675 | |
|
|
676 | $tagged = CBOR::XS::tag $tag, $value |
|
|
677 | This function(!) creates a new "CBOR::XS::Tagged" object using the |
|
|
678 | given $tag (0..2**64-1) to tag the given $value (which can be any |
|
|
679 | Perl value that can be encoded in CBOR, including serialisable Perl |
|
|
680 | objects and "CBOR::XS::Tagged" objects). |
|
|
681 | |
|
|
682 | $tagged->[0] |
|
|
683 | $tagged->[0] = $new_tag |
|
|
684 | $tag = $tagged->tag |
|
|
685 | $new_tag = $tagged->tag ($new_tag) |
|
|
686 | Access/mutate the tag. |
|
|
687 | |
|
|
688 | $tagged->[1] |
|
|
689 | $tagged->[1] = $new_value |
|
|
690 | $value = $tagged->value |
|
|
691 | $new_value = $tagged->value ($new_value) |
|
|
692 | Access/mutate the tagged value. |
|
|
693 | |
|
|
694 | EXAMPLES |
|
|
695 | Here are some examples of "CBOR::XS::Tagged" uses to tag objects. |
|
|
696 | |
|
|
697 | You can look up CBOR tag value and emanings in the IANA registry at |
|
|
698 | <http://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml>. |
|
|
699 | |
|
|
700 | Prepend a magic header ($CBOR::XS::MAGIC): |
|
|
701 | |
|
|
702 | my $cbor = encode_cbor CBOR::XS::tag 55799, $value; |
|
|
703 | # same as: |
|
|
704 | my $cbor = $CBOR::XS::MAGIC . encode_cbor $value; |
|
|
705 | |
|
|
706 | Serialise some URIs and a regex in an array: |
|
|
707 | |
|
|
708 | my $cbor = encode_cbor [ |
|
|
709 | (CBOR::XS::tag 32, "http://www.nethype.de/"), |
|
|
710 | (CBOR::XS::tag 32, "http://software.schmorp.de/"), |
|
|
711 | (CBOR::XS::tag 35, "^[Pp][Ee][Rr][lL]\$"), |
|
|
712 | ]; |
|
|
713 | |
|
|
714 | Wrap CBOR data in CBOR: |
|
|
715 | |
|
|
716 | my $cbor_cbor = encode_cbor |
|
|
717 | CBOR::XS::tag 24, |
|
|
718 | encode_cbor [1, 2, 3]; |
|
|
719 | |
|
|
720 | TAG HANDLING AND EXTENSIONS |
|
|
721 | This section describes how this module handles specific tagged values |
|
|
722 | and extensions. If a tag is not mentioned here and no additional filters |
|
|
723 | are provided for it, then the default handling applies (creating a |
|
|
724 | CBOR::XS::Tagged object on decoding, and only encoding the tag when |
|
|
725 | explicitly requested). |
|
|
726 | |
|
|
727 | Tags not handled specifically are currently converted into a |
|
|
728 | CBOR::XS::Tagged object, which is simply a blessed array reference |
|
|
729 | consisting of the numeric tag value followed by the (decoded) CBOR |
|
|
730 | value. |
|
|
731 | |
|
|
732 | Future versions of this module reserve the right to special case |
|
|
733 | additional tags (such as base64url). |
|
|
734 | |
|
|
735 | ENFORCED TAGS |
|
|
736 | These tags are always handled when decoding, and their handling cannot |
|
|
737 | be overridden by the user. |
|
|
738 | |
|
|
739 | 26 (perl-object, <http://cbor.schmorp.de/perl-object>) |
|
|
740 | These tags are automatically created (and decoded) for serialisable |
|
|
741 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
|
|
742 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
|
|
743 | |
|
|
744 | 28, 29 (shareable, sharedref, <http://cbor.schmorp.de/value-sharing>) |
|
|
745 | These tags are automatically decoded when encountered (and they do |
|
|
746 | not result in a cyclic data structure, see "allow_cycles"), |
|
|
747 | resulting in shared values in the decoded object. They are only |
|
|
748 | encoded, however, when "allow_sharing" is enabled. |
|
|
749 | |
|
|
750 | Not all shared values can be successfully decoded: values that |
|
|
751 | reference themselves will *currently* decode as "undef" (this is not |
|
|
752 | the same as a reference pointing to itself, which will be |
|
|
753 | represented as a value that contains an indirect reference to itself |
|
|
754 | - these will be decoded properly). |
|
|
755 | |
|
|
756 | Note that considerably more shared value data structures can be |
|
|
757 | decoded than will be encoded - currently, only values pointed to by |
|
|
758 | references will be shared, others will not. While non-reference |
|
|
759 | shared values can be generated in Perl with some effort, they were |
|
|
760 | considered too unimportant to be supported in the encoder. The |
|
|
761 | decoder, however, will decode these values as shared values. |
|
|
762 | |
|
|
763 | 256, 25 (stringref-namespace, stringref, |
|
|
764 | <http://cbor.schmorp.de/stringref>) |
|
|
765 | These tags are automatically decoded when encountered. They are only |
|
|
766 | encoded, however, when "pack_strings" is enabled. |
|
|
767 | |
|
|
768 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
|
|
769 | This tag is automatically generated when a reference are encountered |
|
|
770 | (with the exception of hash and array references). It is converted |
|
|
771 | to a reference when decoding. |
|
|
772 | |
|
|
773 | 55799 (self-describe CBOR, RFC 7049) |
|
|
774 | This value is not generated on encoding (unless explicitly requested |
|
|
775 | by the user), and is simply ignored when decoding. |
|
|
776 | |
|
|
777 | NON-ENFORCED TAGS |
|
|
778 | These tags have default filters provided when decoding. Their handling |
|
|
779 | can be overridden by changing the %CBOR::XS::FILTER entry for the tag, |
|
|
780 | or by providing a custom "filter" callback when decoding. |
|
|
781 | |
|
|
782 | When they result in decoding into a specific Perl class, the module |
|
|
783 | usually provides a corresponding "TO_CBOR" method as well. |
|
|
784 | |
|
|
785 | When any of these need to load additional modules that are not part of |
|
|
786 | the perl core distribution (e.g. URI), it is (currently) up to the user |
|
|
787 | to provide these modules. The decoding usually fails with an exception |
|
|
788 | if the required module cannot be loaded. |
|
|
789 | |
|
|
790 | 0, 1 (date/time string, seconds since the epoch) |
|
|
791 | These tags are decoded into Time::Piece objects. The corresponding |
|
|
792 | "Time::Piece::TO_CBOR" method always encodes into tag 1 values |
|
|
793 | currently. |
|
|
794 | |
|
|
795 | The Time::Piece API is generally surprisingly bad, and fractional |
|
|
796 | seconds are only accidentally kept intact, so watch out. On the plus |
|
|
797 | side, the module comes with perl since 5.10, which has to count for |
|
|
798 | something. |
|
|
799 | |
|
|
800 | 2, 3 (positive/negative bignum) |
|
|
801 | These tags are decoded into Math::BigInt objects. The corresponding |
|
|
802 | "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal |
|
|
803 | CBOR integers, and others into positive/negative CBOR bignums. |
|
|
804 | |
|
|
805 | 4, 5, 264, 265 (decimal fraction/bigfloat) |
|
|
806 | Both decimal fractions and bigfloats are decoded into Math::BigFloat |
|
|
807 | objects. The corresponding "Math::BigFloat::TO_CBOR" method *always* |
|
|
808 | encodes into a decimal fraction (either tag 4 or 264). |
|
|
809 | |
|
|
810 | NaN and infinities are not encoded properly, as they cannot be |
|
|
811 | represented in CBOR. |
|
|
812 | |
|
|
813 | See "BIGNUM SECURITY CONSIDERATIONS" for more info. |
|
|
814 | |
|
|
815 | 30 (rational numbers) |
|
|
816 | These tags are decoded into Math::BigRat objects. The corresponding |
|
|
817 | "Math::BigRat::TO_CBOR" method encodes rational numbers with |
|
|
818 | denominator 1 via their numerator only, i.e., they become normal |
|
|
819 | integers or "bignums". |
|
|
820 | |
|
|
821 | See "BIGNUM SECURITY CONSIDERATIONS" for more info. |
|
|
822 | |
|
|
823 | 21, 22, 23 (expected later JSON conversion) |
|
|
824 | CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore |
|
|
825 | these tags. |
|
|
826 | |
|
|
827 | 32 (URI) |
|
|
828 | These objects decode into URI objects. The corresponding |
|
|
829 | "URI::TO_CBOR" method again results in a CBOR URI value. |
378 | |
830 | |
379 | CBOR and JSON |
831 | CBOR and JSON |
380 | CBOR is supposed to implement a superset of the JSON data model, and is, |
832 | CBOR is supposed to implement a superset of the JSON data model, and is, |
381 | with some coercion, able to represent all JSON texts (something that |
833 | with some coercion, able to represent all JSON texts (something that |
382 | other "binary JSON" formats such as BSON generally do not support). |
834 | other "binary JSON" formats such as BSON generally do not support). |
… | |
… | |
421 | Also keep in mind that CBOR::XS might leak contents of your Perl data |
873 | Also keep in mind that CBOR::XS might leak contents of your Perl data |
422 | structures in its error messages, so when you serialise sensitive |
874 | structures in its error messages, so when you serialise sensitive |
423 | information you might want to make sure that exceptions thrown by |
875 | information you might want to make sure that exceptions thrown by |
424 | CBOR::XS will not end up in front of untrusted eyes. |
876 | CBOR::XS will not end up in front of untrusted eyes. |
425 | |
877 | |
|
|
878 | BIGNUM SECURITY CONSIDERATIONS |
|
|
879 | CBOR::XS provides a "TO_CBOR" method for both Math::BigInt and |
|
|
880 | Math::BigFloat that tries to encode the number in the simplest possible |
|
|
881 | way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag |
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|
882 | 4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers |
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|
883 | (Math::BigRat, tag 30) can also contain bignums as members. |
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|
884 | |
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|
885 | CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent |
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|
886 | bigfloats (tags 5 and 265), but it will never generate these on its own. |
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|
887 | |
|
|
888 | Using the built-in Math::BigInt::Calc support, encoding and decoding |
|
|
889 | decimal fractions is generally fast. Decoding bigints can be slow for |
|
|
890 | very big numbers (tens of thousands of digits, something that could |
|
|
891 | potentially be caught by limiting the size of CBOR texts), and decoding |
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|
892 | bigfloats or arbitrary-exponent bigfloats can be *extremely* slow |
|
|
893 | (minutes, decades) for large exponents (roughly 40 bit and longer). |
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|
894 | |
|
|
895 | Additionally, Math::BigInt can take advantage of other bignum libraries, |
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|
896 | such as Math::GMP, which cannot handle big floats with large exponents, |
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|
897 | and might simply abort or crash your program, due to their code quality. |
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|
898 | |
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|
899 | This can be a concern if you want to parse untrusted CBOR. If it is, you |
|
|
900 | might want to disable decoding of tag 2 (bigint) and 3 (negative bigint) |
|
|
901 | types. You should also disable types 5 and 265, as these can be slow |
|
|
902 | even without bigints. |
|
|
903 | |
|
|
904 | Disabling bigints will also partially or fully disable types that rely |
|
|
905 | on them, e.g. rational numbers that use bignums. |
|
|
906 | |
426 | CBOR IMPLEMENTATION NOTES |
907 | CBOR IMPLEMENTATION NOTES |
427 | This section contains some random implementation notes. They do not |
908 | This section contains some random implementation notes. They do not |
428 | describe guaranteed behaviour, but merely behaviour as-is implemented |
909 | describe guaranteed behaviour, but merely behaviour as-is implemented |
429 | right now. |
910 | right now. |
430 | |
911 | |
… | |
… | |
437 | Only the double data type is supported for NV data types - when Perl |
918 | Only the double data type is supported for NV data types - when Perl |
438 | uses long double to represent floating point values, they might not be |
919 | uses long double to represent floating point values, they might not be |
439 | encoded properly. Half precision types are accepted, but not encoded. |
920 | encoded properly. Half precision types are accepted, but not encoded. |
440 | |
921 | |
441 | Strict mode and canonical mode are not implemented. |
922 | Strict mode and canonical mode are not implemented. |
|
|
923 | |
|
|
924 | LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
|
|
925 | On perls that were built without 64 bit integer support (these are rare |
|
|
926 | nowadays, even on 32 bit architectures, as all major Perl distributions |
|
|
927 | are built with 64 bit integer support), support for any kind of 64 bit |
|
|
928 | integer in CBOR is very limited - most likely, these 64 bit values will |
|
|
929 | be truncated, corrupted, or otherwise not decoded correctly. This also |
|
|
930 | includes string, array and map sizes that are stored as 64 bit integers. |
442 | |
931 | |
443 | THREADS |
932 | THREADS |
444 | This module is *not* guaranteed to be thread safe and there are no plans |
933 | This module is *not* guaranteed to be thread safe and there are no plans |
445 | to change this until Perl gets thread support (as opposed to the |
934 | to change this until Perl gets thread support (as opposed to the |
446 | horribly slow so-called "threads" which are simply slow and bloated |
935 | horribly slow so-called "threads" which are simply slow and bloated |